Transmission with durability enhancement techniques
The present disclosure relates to durability enhancement techniques for a dry-clutch vehicle transmission. A cooling system that provides a direct convective cooling path to friction surfaces is disclosed. Also disclosed is a continuously variable clutch wear compensation assembly configured to adjust the position of clutch assembly components on-demand or as needed.
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This application is a continuation-in-part and claims the benefit of U.S. Non-Provisional patent application Ser. No. 12/265,283 titled “Temperature Control of Dual Input Clutch Transmission” filed Nov. 5, 2008, now U.S. Pat. No. 8,062,178 which is hereby incorporated by reference in its entirety.
TECHNICAL FIELDThe present disclosure relates to durability enhancement techniques for a dry-clutch vehicle transmission.
BACKGROUNDConventional vehicle transmissions predominantly employ wet clutches to accomplish gear shifting. Transmissions typically include a transmission fluid which is recycled throughout the transmission. Wet clutches generally provide greater heat transfer and temperature control than dry clutches. Wet clutches also, however, have a lower coefficient of friction than dry clutches. Wet clutches are further known to slip pre-engagement as wet clutches have a lower coefficient of friction.
Dry clutches tend to provide higher coefficients of friction than wet clutches. Dry clutches can provide lower costs and complexity. Still, dry clutches can have thermal management and durability issues. Some powershift dry dual-clutch transmissions (or “DCTs”) comprise a manual clutch construction, e.g., as disclosed in U.S. Patent Publication No. 2010/0113216 titled “Temperature Control of Dual Input Clutch Transmission.” Two clutches are utilized to provide functionality closer to that of an automatic transmission clutch vehicle launch. Temperature can significantly impact the length of service life of a transmission in which each input clutch is a dry clutch. A friction surface—the primary source of heat for the transmission—is surrounded by material and lacks a direct convection path for cooling. The transmission has heavy components with high inertia and low heat dissipation. Though the use of a controlled fan can improve cooling in the transmission, the indirect air flow path from the fan to the heat source slows down the cooling process.
Another common issue in dry-clutch transmissions is that clutch wear can be significantly increased by high operating temperatures. Repetitive engagement of clutch components can cause wear on the friction plate. This wear can decrease clutch lifespan. Some existing transmissions have a clutch adjustment mechanism that iteratively adjusts the position of the pressure plate when the clutch becomes slow to engage. Once a maximum distance for clutch engagement is detected the system moves clutch components into a tighter relative position. Since the adjustment is stepwise, the system repetitively over- and under-adjusts both after adjustment and before re-adjustment, respectively. A more efficient method of clutch adjustment is desired. Additionally, a more robust and reversible design is preferred.
Therefore, it is desirable to have a dry-clutch transmission with improved durability and wear reduction techniques. Cooling techniques which provide a more direct convection and conductive path are needed to reduce overheating in the transmission. Moreover, a continuously variable clutch wear compensation assembly is desirable to have a more flexible yet, effective and robust clutch wear adjustment mechanism.
SUMMARYThe present invention addresses at least one or more of the above-mentioned issues. Other features and/or advantages may become apparent from the description which follows.
Certain embodiments of the present invention relate to a dry-clutch transmission, having: a clutch assembly; and a cooling system, including: a hub onto which the clutch assembly is journaled, the hub having a plurality of apertures directed toward friction surfaces in the clutch assembly; a fan configured to direct air through the hub; and a controller configured to control the fan according to a clutch temperature.
Another exemplary embodiment of the present invention relates to a dry-clutch transmission, including: a clutch assembly; and a divider plate included in the clutch assembly having a plurality of airfoil ribs formed on a surface of the plate. A leading edge of at least one of the airfoil ribs is aligned within 60 degrees of a relative vector equal to the sum of an air speed vector and a clutch speed vector.
Another exemplary embodiment of the present invention relates to a dry-clutch transmission, with: a clutch assembly having a pressure plate; and a clutch compensation assembly including: an electric motor; a cam interface between the pressure plate and motor, the motor configured to move the cam interface; and a controller configured to control the electric motor.
Another exemplary embodiment of the present invention relates to a clutch compensation assembly, having: an actuator configured to continuously adjust the position of a clutch pressure plate on an as-needed basis.
Yet another exemplary embodiment of the present invention relates to a transmission control unit, having: fan control logic configured to control a fan according to an inferred clutch temperature; and clutch wear compensation logic configured to adjust clutch pressure plate position according to a clutch actuation condition.
One advantage of the present disclosure is that it teaches cooling techniques that force flow close to the friction surface—a primary source of heat for the transmission—in order to reduce temperature response time to heat events. In some embodiments, the hub includes nozzles of various sizes to force more air towards hotter plates (e.g., friction plates located in the middle of the clutch pack).
Another advantage of the present disclosure is that it teaches a cooling system having inlet and outlet air thermostats giving feedback for software error reduction (such as inferred temperatures) and thermal model reset. This information yields improved shift and launch feel for better clutch torque accuracy through reduced coefficient of friction variation and avoidance of higher temperature levels.
Another advantage of the present teachings is that they enable a dry-clutch transmission to run a longer cooling duty cycle than cooling oil. The cooling duty cycle is improved because the fan is used on-demand which can increase energy and fuel efficiency.
Another advantage of the present disclosure is that it teaches the use of spacers shaped like airfoils aligned with relative air velocity to assist flow thus further contributing to clutch cooling.
Yet another benefit of the present disclosure is that the continuously variable, electric wear adjustment assemblies taught are more robust than a mechanical or iterative system. Moreover the continuously variable system is reversible for error correction enabling better clutch torque accuracy and efficiency during engagement.
In the following description, certain aspects and embodiments will become evident. It should be understood that the invention, in its broadest sense, could be practiced without having one or more features of these aspects and embodiments. It should be understood that these aspects and embodiments are merely exemplary and explanatory and are not restrictive of the invention.
The invention will be explained in greater detail below by way of example with reference to the figures, in which the same references numbers are used in the figures for identical or essentially identical elements. The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. In the figures:
Although the following detailed description makes reference to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly.
Referring to the drawings wherein like characters represent the same or corresponding parts throughout the several views there are shown various exemplary systems for reducing transmission wear and enhancing transmission durability. The systems are best appreciated in a powershift dry dual-clutch transmissions (or “DCTs”) where cooling and wear can be significant issues for the transmission. Though the illustrated examples regard powershift DCTs, the present teachings can be implemented on different kinds of vehicle transmissions including, but not limited to, single-clutch manual transmissions, automatic transmissions, or wet-clutch transmissions. A cooling system is provided that enables a more direct cooling path to the clutch surface thus improving fan efficiency and reducing cooling response time. The fan helps in achieving a more concentrated, forced flow improving heat transfer. This is accomplished, in part, by running the air as close as possible to the heat source (i.e., the friction surfaces in the clutch assembly). The fan is linked to a controller that is responsive to transmission temperatures. Multiple thermocouples are dispersed throughout the transmission to give feedback to the fan controller as to the thermal conditions of the transmission during operation.
Some of the disclosed techniques also improve transmission durability through the implementation of a continuously variable clutch compensation assembly. Instead of iterative adjustments of clutch components, the system continuously adjusts clutch components as-needed. Adjustments are reversible.
Referring now to
The transmission 10, of
Now with reference to
Clutch assembly 20, as shown in
Fan speed can be increased and decreased according to predetermined conditions. Fan 100 is linked to the electric motor 110 and controller 120 as shown in
Two thermocouples 260 and 270 are positioned in the transmission, as shown in
The cooling system 90, as particularly shown in
The clutch assembly 20 further includes a series of separator or divider plates 400, as shown in
Referring now to
The clutch compensation assembly 500, of
Referring now to
The clutch compensation assembly 700, of
While cam interfaces 580 and 770 are shown as two mating ramped surfaces, any number of cams can be incorporated in the clutch compensation assembly to enable continuous variation of clutch position. For example, in one embodiment, the pressure plate is configured with a pinion gear. A worm gear is coupled to an electric motor. The motor directly controls pressure plate position. Other cams including, for example, linkages and rotating cams can be married with the present teachings.
With reference to
Referring now to
In
Thermocouple readings can be used to infer clutch temperature for the controller or send warning signals when transmission temperatures exceed a predetermined threshold. The temperature difference between thermocouples can be used to detect the heat generated by clutch assembly. Moreover, the temperature of the critical clutch surfaces is inferred. Input information supplied to the TCU includes engine speed, engine torque, input clutch speed and input clutch torque. Temperature is inferred from the relative speed between the engine and clutch or clutch slip. The power distribution or energy transfer rate is derived from clutch slip and used to infer temperature as disclosed in U.S. Patent Publication No. 2010/0113216 titled “Temperature Control of Dual Input Clutch Transmission.” Additional input information supplied to the TCU includes the specific heat of the clutches, the rate of heat convection from the clutches, and the weight and thermal conductivity of the clutches, the ambient temperature, coefficient of friction of the clutch surfaces, and initial temperature of the clutches. TCU is configured to process this data in order to calculate the rate of change of rotating power absorbed by the clutches. In another embodiment, measurements from the thermocouples are used to derive clutch temperature. The difference in temperature readings between two or more thermocouples (e.g., 260 and 270 as shown in
Exemplary clutch wear compensation logic 1020, as shown in
Other clutch actuation conditions can be programmed into the logic of
It will be apparent to those skilled in the art that various modifications and variations can be made to the methodologies of the present invention without departing from the scope its teachings. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the teachings disclosed herein. It is intended that the specification and examples be considered as exemplary only.
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
Claims
1. A dry-clutch transmission, comprising:
- a clutch assembly;
- a cooling system, including: a hub onto which the clutch assembly is journaled, the hub having apertures directed toward friction surfaces in the clutch assembly, the apertures being larger at a center than at opposite ends of the clutch assembly; a fan configured to direct air through the hub; and a controller configured to control the fan according to a clutch temperature.
2. The transmission of claim 1, wherein the controller is configured to increase fan speed when the clutch temperature exceeds a predetermined threshold.
3. The transmission of claim 2, wherein the controller is configured to send a warning signal to a user interface when the clutch temperature exceeds another predetermined threshold.
4. The transmission of claim 1, wherein the controller is configured to decrease fan speed when the clutch temperature falls below a predetermined threshold.
5. The transmission of claim 1, further comprising:
- a divider plate included in the clutch assembly having a plurality of airfoil ribs formed on a surface of the plate.
6. The transmission of claim 5, wherein a leading edge of at least one of the airfoil ribs is aligned with a relative vector equal to the sum of an air speed vector and a clutch speed vector.
7. A dry-clutch transmission, comprising:
- a clutch assembly; and
- a divider plate included in the clutch assembly having a plurality of airfoil Ribs formed on a surface of the plate;
- wherein a leading edge of at least one of the airfoil ribs is aligned within 60 degrees of a relative vector equal to the sum of an air speed vector and a clutch speed vector.
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Type: Grant
Filed: Oct 2, 2010
Date of Patent: Dec 30, 2014
Patent Publication Number: 20110024258
Assignee: Ford Global Technologies, LLC (Dearborn, MI)
Inventors: Eli Avny (Ypsilanti, MI), Matthew John Shelton (Grosse Ile, MI), Steven Gerald Thomas (Bloomfield Hills, MI)
Primary Examiner: Troy Chambers
Assistant Examiner: Ryan Dodd
Application Number: 12/896,877
International Classification: F16D 13/72 (20060101);